During the past year, we have continued investigations in two of the original three project areas. We have examined the proliferation of acute nonlymphocytic leukemia cells after a 30 min exposure to 10-6 M 12-0-tetradecanoyl-phorbol-13-acetate (TPA) and found marked decrease in proliferationof acute myelogenous leukemia (AML) and acute myelomonocytic leukemia (AMML) cells. We did not find that repeat surface antigen profile determination 3 days after TPA treatment was helpful in classifying cells of different leukemias because of the paucity of viable remaining cells at 3 days. Because of the marked decrease in proliferation of certain leukemic cells, we have begun a new clinical protocol using reinfusion of TPA-treated autologous marrow for patients in second remission of AML or AMML. Only patients whose cells cease proliferation after exposure to TPA areeligible. We have found that leukemic blast cells do not regain proliferative capacity after TPA exposure, that normal granulocyte-macrophage colony forming units continue to grow from TPA-treated marrow, and that in the two patients studied autologous TPA-treated marrow was capable of repopulating the marrow. We have also continued studies on colony stimulating activity (CSA) production by T-cell subsets. We found it more efficient to purify the subsets using a column of antibody-coupled Sepharose 6-MB rather than the FACS. We found a less than 5% contamination with the undesired subset. Preliminary studies indicated that the OKT4+ subset, stimulated by PHA, produced as much CSA as the unseparated T cells with no contribution from OKT8+ cells. We plan to repeat these studies using the monokine described by Bagby et al. as the stimulant. (M)